Liquid chemical distribution method and apparatus

ABSTRACT

A chemical solution distribution system and method that includes or employs a plurality of liquid handlers where each of the liquid handlers includes a movable table that engages a sample multiwell plate and can align pipettes of the station with different subsets of wells of the multiwell plate where the number of wells of the multiwell plate is a multiple of the number of pipettes of the head of the pipette station. The system further includes and employs four different pumps to enable the system and method to supply four different solutions to wash stations of each of the four liquid handlers.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of an earlier filing date under 35U.S.C., Section 120 to a patent application identified as Ser. No.08/858,016, filed May 16, 1997, now U.S. Pat. No. 5,985,214 entitled,Systems and Methods for Rapidly Identifying Useful Chemicals in LiquidSamples by Stylli et al., of which the present application is acontinuation in part.

TECHNICAL FIELD

The present invention generally relates to automated systems and methodsfor processing chemicals dissolved in solvents and for rapidlyidentifying chemicals with biological or toxic activity in liquidsamples, particularly automated methods of reformating samples and theaspiration and dispensation of potential new medicines, agrochemicals,and cosmetics.

BACKGROUND

Systems and methods for rapidly identifying chemicals with biological ortoxic activity in samples, especially small liquid samples, can benefita number of different fields. For instance, the agrochemical,pharmaceutical, and medical diagnostics fields all have applicationswhere large numbers of liquid samples containing chemicals areprocessed. Currently, many such fields use various strategies to reduceprocessing times, such as simplified chemistry, semi-automation androbotics. While such strategies may improve the processing time for aparticular single type of liquid sample, process step or chemicalreaction, such methods or apparatuses can seldom efficiently processmany thousands of dissimilar samples, for example as found in a chemicallibrary, or in a nucleic acid array. As the size of chemical librariesand nucleic acid arrays has grown, the rate at which complex librariescan be accurately distributed for testing or analysis has becomerate-limiting. In particular, there is a need to develop methods anddevices that can rapidly process many thousands of different samples andaccurately and reproducibly distribute or redistribute known amounts ofthose samples for further analysis. Central to this need is arequirement to efficiently handle a multitude of different liquidsamples, such as chemical or nucleic acid libraries present in chemicalor sample multiwell plates of varying densities and formats.

Multiwell plates may be orientated and configured in a variety ofdesigns and formats and be present either with, or without, lids. Forexample, multiwell plates, commonly known as “microplates”, have been incommon use for decades with a predominant format being a molded plasticmultiwell plate having 96 sample wells in an 8×12 rectangular array.Typical well volumes are 200 or 300 microliters, depending upon themanufacturer and model of multiwell plate, although other volumes may beprovided for specific uses, for example see Whatman/Polyfiltronics 1998Microplate Product Guide. Polyfiltronics Inc., 136 Weymouth Street,Rockland, Mass. 02370 USA. A proposed standard, designated “Microplate96-Well Standard” (MP96) has been promulgated by The Society forBiomolecular Screening, as published in Journal of BiomolecularScreening, Volume 1, Number 4, 1996, the disclosure of which isincorporated herein by reference. A multiwell plate which meets thegeneral dimensional requirements of the standard is designated MP96-3.Typically, each multiwell plate manufacturer will also provide acompatible lid. A typical lid comprises a generally rectangular flatplanar top surrounded by a flange depending from the top along its sidesand edges.

Multiwell plates are used for many different types of applications,including chemical library generation and storage, additionallymultiwell plates may also be used to hold arrays of polynucleotides foruse in expression analysis, or genomic analysis, as described in forexample, Schena (1996) Genome analysis with gene expression microarraysBioEssays 18 no 5 427-431; Johnson (1998), Gene chips: Array of hope forunderstanding gene regulation Current Biology 8 R171-R174; Scholler etal. (1998) Optimization and automation of fluorescence-based DNAhybridization for high-throughput clone mapping Electrophoresis 19504-508. Multiwell plates may also be used for gene amplification usingthe polymerase chain reaction as described in U.S. Pat. No. 5,545,528entitled Rapid Screening Method of Gene Amplification Products inPolypropylene Plates.

The advent of high throughput analysis and increasing use ofminiaturized formats has also lead to the development of higher formatmultiwell plates for example, 384, 864 and 3456 wells as described inPCT patent application identified by serial number PCT/US98/11061entitled Low Background Multi-Well Plates With Greater Than 864 Wellsfor Fluorescence Measurements of Biological and Biochemical Samples,published Dec. 2, 1998. Even higher density sample processing systems,for example using chips that contain miniaturized microfluidic devicesare being developed (see for example, Marshall (1998) Lab-on-a Chip:Biotech's Next California Gold Rush R & D Magazine, November 1998, pages38 to 43).

Higher density multiwell plates enable faster analysis and handling oflarge sample or chemical libraries, such as in automated screeningsystems. However, irrespective of the final plate density, the inventorshave often recognized that the overall throughput of the system islimited by the requirement to distribute chemical solutions frommultiwell plates with a first well density to a second well density,particularly when the second well density is greater than 96 wells perplate. The need thus exists for a chemical solution distribution systemthat can rapidly and accurately process liquid samples on multiwellplates of different densities, particularly those with densities ofgreater than 96 wells per plate.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram of an embodiment of a chemical solution distributionsystem according to the present invention.

FIG. 2 is a diagram of the main section of the chemical solutiondistribution system shown in FIG. 1.

FIG. 3 is a diagram of a segment of the main section of the chemicalsolution distribution mechanically connected to a conveyor system toillustrate the bar code reader section.

FIG. 4 is a diagram of an exemplary liquid handler or liquid handlingaccording to the present invention and shown in FIG. 1 and FIG. 2.

FIG. 5A is a partial diagram of an exemplary 384-well sample or chemicalplate.

FIG. 5B is a section A—A of the exemplary 384-well chemical plate shownin FIG. 5A.

FIG. 6A (perspective view of assembled unit) and B (exposed view of onebank) shows components of another embodiment of a chemical solutiondistribution apparatus.

FIG. 7 shows different well densities in relation to different tippositions of a pipette array.

SUMMARY

In one embodiment, the invention is a chemical solution distributionsystem capable of rapidly distributing liquid samples between aplurality of multiwell plates including a first multiwell plate having adifferent number of wells from a second multiwell plate. The secondplate having a number of wells greater than the number of the pipettesin a head of a liquid handler, typically in a defined pre-set matrix ofimmobile pipettes. In particular, one embodiment is directed tomultiwell plates having a number of wells that are a multiple of thenumber of pipettes in a head of a liquid handler. The system typicallydistributes samples between a plurality of multiwell plates having Nwells where the number of pipettes in a liquid handler is M. M is aninteger multiple, I of N. Each of the plurality of multiwell plates isthus comprised of I subsets of M wells, N total (M*I wells). In thisembodiment, the system includes a plurality of liquid handlers to enableparallel processing of multiwell plates. Each liquid handler includes ahead movable in a Z-direction with M pipettes and a table configured toengage one of the plurality of multiwell plates and move in an X-Y planerelative to Z. Typically, the table is movable to at least I differentpositions. In each of the I positions, typically a different subset of Mwells of the multiwell plates are aligned with the M pipettes of thehead of the station. Such a chemical solution distribution system issuited for rapidly distributing samples of chemicals where the multiwellplates are chemical libraries or master multiwell plates. Also, in apreferred embodiment the system has I liquid handlers corresponding tothe I subsets of M wells of each of the plurality of multiwell plates.In this embodiment, each liquid handler further includes a wash stationbelow the head. In each station, typically the head is able to move theM pipettes in the Z-direction into contact with solution in the washstation. In addition, the system may include a different wash stationsolution pump for each liquid handler. Each pump is capable ofdelivering or providing a different solution to the wash station of eachliquid handler. In order to improve the efficiency of the distributionsystem, the system may further include at least one multiwell platestacker or buffer. The stacker is capable of storing a plurality ofmultiwell plates and enables adaptive routing of multiwell plates fromthe chemical solution distribution system to other system modules. Inorder to transfer a multiwell plate from the multiwell plate stacker toa liquid handler, the system may further include a multilane conveyingsystem to enable parallel adaptive processing of multiwell plates. Insome embodiments, the multiwell plates may have lids. In such a case,the system may further include a delidder capable or removing andreplacing lids on plates. Typically, the multilane conveying system alsocommunicates multiwell plates to a delidder.

In one exemplary embodiment, the system separately processes multiwellliquids in plates having 96 wells into plates with 384 wells, N equal to384, and having 96 pipette heads in each liquid handler, M equal to 96while maintaining the integrity, or discrete nature, of each solution.In this embodiment, there are typically four liquid handlers, one foreach of the four subsets (I equal to 4), of 96 wells of the 384 wellplates. This increases the efficiency of the chemical solutiondistribution system. In other embodiments, the system may be designed toprocess up to 864 well plates. Further, the system may also process 96well plates while simultaneously being able to process higher densitywell (greater than 96 well) plates, such as 384 well plates. In such anembodiment, the table in each liquid handler is capable of aligning thepipettes with the wells of the 96 well plates and larger well (greaterthan 96 well) plates.

The present invention also includes a method of distributing chemicalsolutions, between N well plates. As above, each N well plate isconsidered to have I subsets of M wells where I*M equals N. One methodincludes aligning a subset of M wells of a first N-well plate with Mpipettes of a first pipette station and aligning a subset of M wells ofa second N-well plate with M pipettes of a second pipette station. Themethod further includes lowering the M pipettes of the first pipettestation to within a desired distance of the subset of M wells of thefirst N-well plate and then either aspirating solution from M wells intothe M pipettes or dispensing solution from the M pipettes into the Mwells. The method also includes lowering the M pipettes of the secondpipette station to within a desired distance of the subset of M wells ofthe second N-well plate and then either aspirating solution from M wellsinto the M pipettes or dispensing solution from the M pipettes into theM wells. The method may further include aligning a subset of M wells ofa third N-well plate with M pipettes of a third pipette station andaligning a subset of M wells of a fourth N-well plate with M pipettes ofa fourth pipette station. This method further includes lowering the Mpipettes of the third pipette station to within a desired distance ofthe subset of M wells of the third N-well plate and then eitheraspirating solution from M wells into the M pipettes or dispensingsolution from the M pipettes into the M wells. This method also includeslowering the M pipettes of the fourth pipette station to within adesired distance of the subset of M wells of the fourth N-well plate andthen either aspirating solution from M wells into the M pipettes ordispensing solution from the M pipettes into the M wells.

In another method of the present invention, the above-described methodmay be applied to a single N-well plate. In such an embodiment, adifferent subset of M wells of the N-well plate may be addressed by theM pipettes of each of the first, second, third, and fourth liquidhandlers. Each of these stations may aspirate or dispense solutionbetween the subset of M wells of the single N-well plate. In theembodiment where N is equal to four times M, the four liquid handlersmay be employed to sample or dispense solution between each of the Nwells of the single N-well plate according to this method.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Generally, the nomenclatureused herein and many of the automation, computer, detection, chemistryand laboratory procedures described below are those well known andcommonly employed in the art. Standard techniques are usually used forengineering, robotics, informatics, optics, molecular biology, computersoftware and integration. Generally, chemical reactions, cell assays andenzymatic reactions are performed according to the manufacturer'sspecifications where appropriate. The techniques and procedures aregenerally performed according to conventional methods in the art andvarious general references (see generally, Knuth, Donald E., The Art ofComputer Programming, Volume 1, Fundamental Algorithms, Third Edition(Reading, Mass.: Addison-Wesley, 1997); Volume 2, SeminumericalAlgorithms, Second Edition (Reading, Mass.: Addison-Wesley, 1981);Volume 3, Sorting and Searching, (Reading, Mass.: Addison-Wesley, 1973)for computational methods. For fluorescence techniques see Lakowicz, J.R. Principles of Fluorescence Spectroscopy, New York: Plenum Press(1983) and Lakowicz, J. R. Emerging applications of fluorescencespectroscopy to cellular imaging: lifetime imaging, metal-ligand probes,multi-photon excitation and light quenching. Scanning Micro. Suppl Vol.10 (1996) pages 213-24. For molecular biology and cell biology methodssee Sambrook et al. Molecular Cloning. A Laboratory Manual, 2d ed.(1989) Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. andSpector et al. Cells a Laboratory Manual, first ed. (1998) Cold SpringHarbor Laboratory Press, Cold Spring Harbor, N.Y. For general opticalmethods see Optics Guide 5 Melles Griot® Irvine Calif., OpticalWaveguide Theory, Snyder & Love published by Chapman & Hall. For fiberoptic theory and materials see Peter Cheo Fiber Optics Devices andSystems, published by Prentice-Hall, which are incorporated herein byreference which are provided throughout this document). The nomenclatureused herein and the laboratory procedures in chemistry, molecularbiology, automation, computer sciences, and drug discovery describedbelow are those well known and commonly employed in the art. Standardtechniques are often used for chemical syntheses, chemical analyses,drug screening, and diagnosis. As employed throughout the disclosure,the following terms, unless otherwise indicated, shall be understood tohave the following meanings:

“Adaptive routing” refers to a change in the path to be followed by awork unit as a result of conditions encountered during a stage or stagesof processing. Conditions could include results of previous processingsteps, equipment out of order, processing priorities, or other factors.The path is the sequence of steps called for to process a work unit. Forexample, the path is the sequence of steps called for in the assaydefinition, which may be independent of specific processing equipment.System processing is typically performed at workstations, so adaptiverouting allows alternative workstations to be substituted bycomputerized instruction.

“Operably linked” refers to a juxtaposition wherein the components sodescribed are in a relationship permitting them to function in theirintended manner. For instance, two components are mechanically linked bya conveyor means are operably linked.

“Parallel processing” refers to the routing of material flow tofacilitate the simultaneous handling of multiple work units at or withinmultiple workstations. Parallel processing between workstations isaccomplished by maintaining individual work queues within a transportsystem for each workstation, and allowing for many liquid handlingoperations to be performed simultaneously. For example, work units canbe delivered in parallel to each of the workstations disposed on atransport system, while other units are queuing for subsequent operationat those workstations. Transfers from the workstations are also to beaccomplished in this manner. Within workstations, many parallelinstruments can perform work on a number of units simultaneously.Parallel processing of liquid samples refers to the paralleldistribution or redistribution of liquid samples into a plurality ofwells in at least one multiwell plate in a workstation. For instance,four parallel aspirate/dispense devices can simultaneously operate onfour multiwell plates in a workstation. When the term parallelprocessing is used, unless explicitly stated, it does not preclude othertypes of processing, such as serial processing.

“Polynucleotide” refers to a polymeric form of nucleotides of at least10 bases in length, either ribonucleotides or deoxynucleotides or amodified form of either type of nucleotide. The term includes single anddouble stranded forms of DNA.

“Plate” refers to a two dimensional array of addressable wells locatedon a substantially flat surface. Multiwell plates may comprise anynumber of discrete addressable wells, and comprise addressable wells ofany width or depth. Common examples of multiwell plates include 96 wellplates, 384 well plates and 3456 well Nanoplates™. Multiwell plates maycontain either samples or chemicals such as reagents and, or,polynucleotides.

“Sample plate” refers to a plate containing a sample to be processed,such as a sample for testing or synthesis. Sample plates are usuallyused in a reaction module, to permit a chemical reaction, or detectionof an optical property of the sample.

“Chemical plate” refers to a plate containing chemicals and, or,polynucleotides, such as a master plate with stock solutions or adaughter plate with stock solutions or dilutions thereof.

“Solid substrate” refers to a surface onto which a sample or chemicalpresent in solution or suspension could be deposited. Substrates couldinclude the surfaces of silicon or glass chips, or detection surfaces orsensors.

“Sample matrix” refers to a two dimensional array or pattern of samplesites, generally preset.

“Tip dispenser matrix” refers to a two dimensional array or pattern oftip dispensers generally in a preset, immobilized array, usually with atleast 2 to 4 rows and 2 to 4 columns, preferably 12 rows and 8 columnsfor 96 well formats.

Other chemistry terms herein are used according to conventional usage inthe art, as exemplified by The McGraw-Hill Dictionary of Chemical Terms(ed. Parker, S., 1985, McGraw-Hill, San Francisco, incorporated hereinby reference).

Introduction

The present invention is directed towards systems and methods for therapid distribution and redistribution of liquid samples in multiwellplates or onto substrates, typically for reformating chemical libraries.As a non-limiting introduction to the breadth of the invention, theinvention includes several general and useful aspects, including:

1) a system of integrated components for the rapid aspiration anddistribution of liquid samples from multiwell plates of dissimilarformats,

2) a method for reformatting the position of liquid samples present inmultiwell plates.

3) a system for the rapid distribution of liquid samples to multiwellplates, and

4) a system of distributing samples, such as chemicals dissolved in asolvent, into an array or matrix on a substrate.

These aspects of the invention, as well as others described herein, canbe achieved by using the devices and methods described herein. To gain afull appreciation of the scope of the invention, it will be furtherrecognized that various aspects of the invention can be combined to makedesirable embodiments of the invention. For example, the inventionincludes a system for the rapid redistribution of liquid samples thatcould be operatively linked to a storage and retrieval module ordetector module. Such combinations result in particularly useful androbust embodiments of the invention.

An exemplary embodiment of chemical solution distribution system 200according to the present invention is presented with reference to FIG.1. The chemical solution distribution system 200 shown in FIG. 1includes four liquid handlers 240, a programmable logic controller(“PLC”) cabinet 282, solution pumps 190 and pump tubing 192, drains 242and drain tubing 243, two plate buffers or stacker stations 260, amultiwell plate delidder/lidder station 250, bar code reader 230,operator console 280, and ingress/egress junction 270. The PLC 282contains the logic controllers that control the operation of the each ofthe components of the system 200 based on operator selections entered onconsole 280. In the preferred embodiment of the invention, console 280is a touch-screen console enabling an operator to view and selectoptions for the control and processing of chemical or sample multiwellplates.

The core of an embodiment of the system 200 is described in more detailwith reference to FIG. 2. The system includes a conveyor means 210 (e.g.at least one continuous conveyor belt), the conveyor means 210 movessample plates 290 between different components of system 200 that mayperform operations on the sample plate 290. In detail, delidder station250 may remove or replace a lid (not shown) of a sample plate 290.Typically in conjunction with logic controllers, delidder station 250tracks each lid removed with the corresponding sample plate 290. Eachliquid handler is designed to either aspirate solutions from wells ofsample plate 290 to pipetting heads or dispense solution from pipettingheads to wells of sample plate 290. Stacker stations 260 stack or bufferplates and can be used to increase the overall efficiency of system 200.To track sample multiwell plates, system 200 includes a bar code reader230 as shown in FIG. 3.

As shown in FIG. 3, an exemplary embodiment of system 200 furtherincludes a photosensor 232, diving board (to ensure smooth transitionfrom the conveyer multiwell plate), 272, and stop pins 212. Photosensor232 detects the present of sample multiwell plates on the conveyor belt210. Upon detection of a sample plate, bar code reader 230 detects anddecodes the bar code on a sample plate on conveyor 210 as is well knownto one of skill in the art. The bar code information of the sample plate290 enables system 200 to track sample plates as they are processed bythe system. Upon identification of the sample plate 290, system maydirect the conveyor 210 to transfer the multiwell plate to one of theprocessing components, i.e., delidder station 250, liquid handlers 240,and stacker station 260. The diving board 272 which is part ofingress/egress station 270 enables interconnection of system 200 as partof an automated screening system 300, such as the system described thePCT application WO 98/52047, entitled Systems and Methods for RapidlyIdentifying Useful Chemicals in Liquid Samples published Nov. 16, 1998which is hereby incorporated by reference.

As part of an automated screening system, system 200 may attach as aworkstation. In a preferred embodiment of the invention, conveyor 210includes two parallel plastic belts that travel along the length of theworkstation (FIG. 2). An AC motor (not shown) turns the belts throughcoordination of photosensors 232, stop pins 212, and logic controller.In detail, in a preferred embodiment sixteen Keyence® Fiber OpticSensors are used to track or check the location of sample plates insystem 200. In addition, thirteen pairs of Clippard® pneumatic actuatorsfunction as stop pins 212 to position sample plates 290 at the eightdifferent stations of system 200 (the stations includes bar code readerstation 230, a delidder station 250, four liquid handlers 240, and twostacker or buffer stations 260.)

In a preferred embodiment of the invention, bar code reader 230 is aMicroscan® MS710 barcode scanner. The reader 230 operates using a 5-voltpower source and may communicate with a personal computer (“PC”) via aRS232 cable. As noted above, delidder station 250, removes and replaceslids of sample plates 290. In detail, delidder 250 removes lids frommultiwell plates 290 entering the system and replaces the lids ofmultiwell plates 290 when they leave system 200. In the exemplaryembodiment, the delidder station 250 includes a magazine for holding upto 60 lids, a lifting device (not shown), and retaining pads (notshown). In operation, the lifting device, located directly below theconveyor 210 employs a bi-directional motor that lowers and raises fourpins. Lids are captured and replaced by delidder 250 by raising andlowering the height of the four pins. Usually, two optical sensors arepositioned below the retaining pads to coordinate the employment of theretaining pads during the movement of a lid. As noted above, system 200also includes two stacker or buffer stations 260 that are used to storemultiwell plates. Storing multiwell plates 290 enables system 200 toperform complex operations on multiwell plates. In an exemplaryembodiment, each stacker may store fifty standard depth multiwell platesor seventeen deep well multiwell plates. Similar to delidder 250, eachstacker or buffer 260 also employs four pins and retaining pads tocapture and transport multiwell plates 290 (instead of lids). In thepreferred embodiment, the lifting devices of the stackers include twoBimba Flat-1 FS 040.5 XH pneumatic actuators. Of the components thatprocess sample multiwell plates 290, liquid handlers 240 perform theprimary function of system 200, i.e., distribution of chemicals orsamples between sample plates 290.

An exemplary liquid handler 240 is presented with reference to FIG. 4.The exemplary pipette station 240 includes a drain 242, wash station245, Z-axis motor 246, pipettes on a head 247, movable table or platen248, and D-axis motor 249. In this embodiment, Z-axis motor 246 controlsthe height of the pipettes 247 relative to the wash station 245 andmultiwell plate 290 when a plate 290 is positioned in a liquid handler240. Alternatively, though not preferred the table can include a Z-axismotor to vary the height. The height of the pipettes relative to themultiwell plate 290 may vary for differently sized multiwell plates withparticular well densities. In an exemplary embodiment, the Z-motor axisis a 1.7 volt 4.7 Amp bi-directional servomotor. The D-axis motor 249 isused to control the amount of solution aspirated into or dispensed frompipettes 247. The D-axis motor 249 is also a 1.7 volt 4.7 Ampbi-directional servo-motor. In detail, the motor is coupled to pistonsthat produce air displacement in pipettes 247 to control aspiration ordispensation of solution. It is noted that the present invention cansupport different pipette types. In this embodiment, each station 260has 96 pipettes in an eight by twelve rectangular configuration.Pipettes 247 are positive displacement fixed probes having 200, 50 or 20microliter capacities. As noted above, each station also has a washstation 245 and drain 242. The wash station includes 96 chimneys thatwell up and spill over when a pump 190 is operating. The overflow spillsinto the drain 242 and then drain tubing 243. In the preferredembodiment, each liquid handler 240 has a different pump 192 enabling adifferent buffer or dimethylsulfoxide (“DMSO”) to be provided by eachwash station 245. This increases the ability of system 200 to performmore complex operations efficiently. Each liquid handler also has anindependently movable platen or table 248. Alternatively, though notpreferred, the liquid handling can move in the X or Y direction, as setforth herein.

The table engages a multiwell plate 290 when it enters a station 240. Asdescribed with reference to FIG. 5A and FIG. 5B, table 248 enables eachliquid handler 240 to process multiwell plates 290 having a number ofwells equal to a multiple of the number of pipettes heads. For example,if a multiwell plate having N wells is to be processed by a stationhaving M pipettes where M is an integer multiple, I of N, then table 248would need to align or address the pipettes with I different subsets ofM wells that comprise the N wells of the multiwell plate to beprocessed. As noted above, exemplary liquid handlers 240 have 96 (M=96)pipettes. Depending on the addressable positions of table 248, eachstation 240 may process sample multiwell plates having a number of wellsequal to an integer multiple of 96. In the preferred embodiment, eachstation 240 may process multiwell plates having 96 or 384 (4*96) wells291.

A partial diagram of an exemplary 384-well sample multiwell plate 290 isshown in FIG. 5A. The multiwell plate is rectangular having a 16 by 24configuration. A standard 96-well plate (not shown) has an 8 by 12configuration. In order to address the 384 wells of a 384-well plate,the plate is subdivided into four (I=4) subsets of 96 wells as shown inFIG. 5B. Table 248 can be positioned to align any subset of 96 wellswith the 96 pipettes. Thus, table 248 may address any of the foursubsets of wells shown as quadrants 292, 293, 294, and 295 in FIG. 5B.FIG. 5B also shows the position 297 of a well of a correspondingstandard 96-well plate is centered relative to the four subsets of 96wells of a 384 well plate. Thus, to address both a standard 96-wellplate and 384-well plates, tables 248 each address five differentpositions: center, upper left quadrant, upper right quadrant, lower leftquadrant, and lower right quadrant. The combination of the movabletables 248 and separate pumps 192 for wash stations 245 of each liquidhandler 240 and conveyor 210 enables system 200 to efficiently handlecomplex operations involving groups of 384-well plates and 96-wellplates simultaneously. For example, four different 384-well plates maybe simultaneously processed by each liquid handler 240. Each station mayalign the 96 pipettes 247 with any of the four subsets of 96 wells ofthe 384 well plates by moving the multiwell plate via table 248. Then,solution may be aspirated from or dispensed to the four, different384-well plates. In another example, four 96-well master plates may besimultaneously processed by the four liquid handlers 240 to aspirate ordispense solution. Also, a single 384-well plate may be processed by allfour liquid handlers 240 in sequential or serial order where eachstation 240 processes a different one of the four subsets of 96-wells byaspirating or dispensing solution in each subset.

FIG. 6A (perspective view of assembled unit) and B (exposed view of onebank) shows components of another embodiment of a sample distributionapparatus that includes valves 1910, valve tips 1920 (straight tip inFIG. 6B, bent tip in FIG. 6A, tip block 1930, valve block 1940, valveblock assembly 1950, fluid lines 1960, and fluid manifold 1970, fluidreservoir 1980, and pressure system are not shown. In a preferredembodiment (48 valve linear array), four linear arrays of 12 valve(banks) each are placed side by side. The valves and pipette tips ineach of these arrays are spaced 6 mm apart and each array is staggered1.5 mm in relation to each other. The tips of the valves are configuredto share the same fluid path configuration and align together into alinear array of 48 tips spaced 1.5 mm apart. The tips from a single bankof valves are spaced 6 mm apart and are arranged as every fourth tip inthe 48-tip array.

Another embodiment uses larger valves that would require larger spacingbetween each valve. The tips in this embodiment would use flexibletubing to connect the valve and tips. Each valve can be individuallycontrolled to allow different patterns of dispensing. Though designed todispense into a 48 well per column plate, this array could also dispenseinto other multiwell plate configurations. For example, 864-well plates(24 by 36 wells), 384-well plates (16 by 24 wells) or 96-well plates (8by 12 wells) are compatible by using every second, third or sixth valve,respectively. If the multiwell plate can be moved in the Y as well asthe X direction, then each 48 valve linear array can dispense up to fourdifferent reagents by plumbing a different reagent into each of the fourbanks of 12 valves. Moving the multiwell plate in both the X and Ydirections allows each well to align with a pipette tip from each bank.If the plate can only be moved in the X direction, then the followingdispensing arrangements are possible with a 48-pipette array (see FIG.7).

96-Well Plate (6.5 mm Diameter Wells) Multiple Reagent Mode

A single 48 valve linear array can deliver up to four different reagentsinto a 96-well plate since a single bank can deliver into each well.Each bank is plumbed to receive a different reagent. Plate can besecured properly in the Y direction for each reagent and the multiwellplate does not need to move in the Y direction during the dispensing ofthat one reagent.

384-Well Plate (3.4 mm Diameter Wells) Single Reagent Mode

Valves from each bank must be used in order to dispense into each wellof a 384-well plate; therefore only one reagent can be dispensed fromthe 48-pipette array.

864-Well Plate (Approximately 2.0 mm Diameter Wells)

Each well can be accessed by using either banks 1 and 3 or banks 2 and4. This allows two different reagents to be delivered if the multiwellplate is aligned properly in the Y direction for each reagent. Inoperation, the linear array of pipettes can be positioned over ahigh-density plate, e.g., 48 by 72-well plate. The wells in thismultiwell plate are spaced identically to the pipettes (1.5 mm apart).The pipettes are activated and a reagent is dispensed simultaneouslyinto each well in one column. The multiwell plate is then moved over onecolumn and the pipettes are again activated. This is repeated over theentire multiwell plate. The amount dispensed is controlled by the valveopening time and the pressure feeding the reagent to the valves (otherfactors also control dispensed volumes, particularly restrictions toflow). Variable amounts can be dispensed into each well by controllingthe timing of valve opening and the dispensation pattern across thelinear array of valves. Each pipette of the linear array can beindividually controlled via software. The entire fluid path can beflushed clean by first purging the four fluid manifolds, followed byeach of the 48 valves. Three 3-way valves (two on the input side and oneon the output side of the fluid manifolds) will allow flushing with awash liquid and with air. The device can be cleaned between reagentchanges and for long-term inactive periods. The valve assembly can bedesigned in a modular form in order to facilitate replacement and repairof single valve/tip components and/or whole banks of valves. The fluidpath dead space is preferably designed to minimize flush out volumes.

In another embodiment, the pipette tip pitch can be modulated via a camshaft mechanism which enables on-the-fly control of pipette tip spacing.

In another embodiment, each valve array can contain a different reagentand address the dispensation requirements of the assay by additionalpositioning movements under the linear array pipette.

In one additional embodiment, the sample distribution apparatus canrapidly dispense or aspirate large numbers of small volume samples,around 10 to 50 nanoliters to, and from, multiwell plates of differentwell densities to enable efficient distribution of chemical samples.

Component Functions

Aspiration or dispensation into multiwell plates of different densitiesis accomplished by automated orthogonal positioning of a multiwell platesuch as shown in FIG. 5A and FIG. 5B. Typically, the multiwell platesare securely disposed on an orthogonal positioner or table 248 thatmoves the wells of a multiwell plate with a first density in an X, Yposition with respect to the X, Y position of the liquid handler.Usually, the liquid handler will have an array of aspiration and/ordispensation pipettes 240.

Many aspiration/dispensation pipettes can operate simultaneously inparallel. The orthogonal positioner will align each well with theappropriate pipetting head. Preferably, a predetermined location (e.g.,center) of a pre-selected addressable well will be aligned with thecenter of pipetting head's fluid trajectory. Other alignments can beused, such as those described in the following examples. With apipetting head substantially smaller than a well diameter, orthogonalpositioning permits aspiration or dispensation into multiwell plates ofdifferent densities and well diameters.

An orthogonal positioner or table can typically match an array ofpipettes with an array of wells in X, Y using a mechanical means to movethe wells into position or the liquid handler (e.g., dispensing heads)into position. Preferably, arrays of wells on a multiwell plate aremoved rather than the liquid handler. This design often improvesreliability, since multiwell plates are usually not as heavy orcumbersome as liquid handlers, which results in less mechanical stresson the orthogonal positioner and greater movement precision. It alsopromotes faster liquid processing times because the relatively lighterand smaller multiwell plates can be moved more quickly and preciselythan a large component. The mechanical means can be a firstcomputer-controlled servo-motor that drives a base disposed on an Xtrack and a second computer-controlled servo motor that drives an Ytrack disposed on the X track. The base can securely dispose a multiwellplate and either a feedback mechanism or an accurate Cartesian mappingsystem, or both that can be used to properly align wells with pipettes.Other such devices, as described herein, known in the art or developedin the future to accomplish such tasks can be used. Usually, suchdevices will have an X, Y location accuracy and precision of at least0.1 mm in X and 0. 1 mm in Y, preferably of at least 0.03 mm in X and0.03 mm in Y, and more preferably of at least 0.01 mm in X and 0.01 mmin Y. It is desirable that such devices comprise detectors to identifythe wells or multiwell plates being orthogonally positioned. Such,positioners for predetermined X, Y coordinates, can be made using leadscrews having an accurate and fine pitch with stepper motors (e.g.,Compumotor Stages from Parker, Rohnert Park, Calif., USA). Such motorscan be computer-controlled with the appropriate electrical inputs to thestepper motor. Orthogonal positioners can be used with other componentsof the invention, such as the reagent pipette or detector to positionsample multiwell plates.

Alternatively, a liquid handler can be disposed on a Z-positioner,having an X, Y positioner for the liquid handler in order to enableprecise X, Y and Z positioning of the liquid handler (e.g., LinearDrives of United Kingdom). A reference point or points (e.g., fiducials)can be included in the set up to ensure that a desired addressable wellis properly matched with a desired addressable head. For instance, themultiwell plate, the orthogonal positioner or the liquid handler caninclude a reference point(s) to guide the X, Y alignment of a multiwellplate, and its addressable wells, with respect to the liquid handler.For example, the liquid handler may have a detector such as a camera(not shown) that corresponds in X, Y to each corner of a multiwellplate. The multiwell plate may have orifices (or marks) that correspondin X, Y to the liquid handler's position detectors. The multiwellplate's orifices allow light to pass or reflect from acomputer-controlled identification light source located on theorthogonal positioner in the corresponding X, Y position. Opticallocators known in the art can also be used in some embodiments, such asdescribed in PCT patent application WO91/17445 (Kureshy), which ishereby incorporated by reference. Detection of light by the liquidhandler emitted by the orthogonal positioner verifies the alignment ofthe multiwell plates. Once multiwell plate alignment is verified,aspiration or dispensation can be triggered to begin. Stepper motors canbe controlled for some applications as described in U.S. Pat. No.5,206,568 (Bjornson), which is hereby incorporated by reference.

When handling multiwell plates of different densities, it is desirableto track the multiwell plate density with a database linked to a platebar code (or some other plate identification system, e.g., radiofrequency) and to provide a sample distribution apparatus that canregister the bar code. Bar code labels are typically positioned on thenarrow end of the multiwell plates, column 12 side, and in a 3 to 1ratio, 0.25″×1.0″, 10 mil bar code 128, such as those from Intermec,Everett, Wash. When used with a data processing and integration modulecontroller, the bar code can easily reference a plurality of multiwellplate and well information from the data store, such that no encodeddata is necessary on the bar code itself. Misread or unreadable labelsproduce an error code available to the supervisory control system. Thesample distribution apparatus can then be properly instructed toaspirate or dispense in a manner that corresponds to the well density ofthe multiwell plate. This permits aspiration at one well density anddispensation at a second well density. Thus, compression of low densitymultiwell plates can occur by the transfer of liquids to a higherdensity multiwell plate and expansion of high density multiwell platescan occur by transfer of liquids to a lower density multiwell plate.This feature advantageously allows a sample distribution apparatus tofunctionally interface with other workstations that may individuallyutilize multiwell plates of different well density. For example,traditional 96-well plates can be used to store chemical solutions inmaster plates in a storage and retrieval module. The sample distributionapparatus may aspirate a predetermined volume of chemical solution fromall the addressable chemical wells of a master plate. The sampledistribution apparatus may then dispense a predetermined volume ofchemical solution into a pre-selected portion of the addressable wellsof a 384 daughter plate (i.e. compression). This process can be repeatedto construct replicate arrays on the same or different daughter plate.

In one embodiment, the liquid handler may comprise a plurality ofnanoliter pipettes that can individually dispense a predeterminedvolume. Typically, pipettes are arranged in two-dimension array tohandle multiwell plates of different well densities (e.g., 96, 384, 864and 3,456). Usually, the dispensed volume will be less thanapproximately 2,000 nanoliters of liquid that has been aspirated from apredetermined selection of addressable chemical wells and dispensed intoa predetermined selection of addressable sample wells. Preferably,nanoliter pipettes can dispense less than approximately 500 nanoliters,more preferably less than approximately 100 nanoliters, and mostpreferably less than approximately 25 nanoliters. Dispensing below 25nanoliters can be accomplished by pipettes described herein. Preferably,minimal volumes dispensed are 5 nanoliters, 500 picoliters, 100picoliters, or 10 picoliters. It is understood that pipettes capable ofdispensing such minimal volumes are also capable of dispensing greatervolumes. The maximal volume dispensed may be largely dependent on thedispense time, reservoir size, tip diameter and pipette type. Maximumvolumes dispensed are about 10.0 microliters, 1.0 microliters, and 200nanoliters. Preferably, such liquid handlers may be capable of bothdispensing and aspirating. Usually, a nanoliter pipette (or smallervolume pipette) comprises a fluid channel to aspirate liquid from apredetermined selection of addressable wells (e.g., chemical wells).Liquid handlers are further described herein, and for some volumes,typically in the microliter range, suitable liquid pipettes known in theart or developed in the future can be used. It may be particularlyuseful to use liquid handlers capable of handling about 1 to 20microliter volumes when it is desired to make daughter plates frommaster plates. Preferably, in such instances a liquid handler has adispensing nozzle that is adapted for dispensing small volumes and cansecure a tip having a fluid reservoir.

In one embodiment, nanoliter pipettes comprise solenoid valves fluidlyconnected to a reservoir for liquid from an addressable chemical well.The fluid reservoir can be a region of a pipette tip that can hold fluidaspirated by the nanoliter pipette. Usually, a tip reservoir may hold atleast about 100 times the minimal dispensation volume to about 10,000times the dispensation volume and more preferably about 250,000 timesthe dispensation volume. The solenoid valves control a positivehydraulic pressure in the reservoir and allow the release of liquid whenactuated. A positive pressure for dispensation can be generated by ahydraulic or pneumatic means, e.g., a piston driven by a motor or gasbottle. A negative pressure for aspiration can be created by a vacuummeans (e.g., withdrawal of a piston by a motor). For greater dispensingcontrol, two solenoid valves or more can be used where the valves are inseries and fluid communication.

In another embodiment, nanoliter pipettes comprise an electricallysensitive volume displacement unit in fluid communication to a fluidreservoir. Typically, the fluid reservoir holds liquid aspirated from anaddressable chemical well. Electrically sensitive volume displacementunits are comprised of materials that respond to an electrical currentby changing volume. Typically, such materials can be piezo materialssuitably configured to respond to an electric current. The electricallysensitive volume displacement unit is in vibrational communication witha dispensing nozzle so that vibration ejects a predetermined volume fromthe nozzle. Preferably, piezo materials are used in pipettes for volumesless than about 10 to 1 nanoliter, and are capable of dispensing minimalvolumes of 500 to 1 picoliter. Piezo pipettes can be obtained fromPackard Instrument Company, Connecticut, USA (e.g., an accessory or theMultiProbe 104). Such devices can also be used in other liquid handlingcomponents described herein depending on the application. Such smalldispensation volumes permit greater dilution and conserve and reduceliquid handling times. In some embodiments, the liquid handler canaccommodate bulk dispensation (e.g., for washing). By connecting a bulkdispensation means to the liquid handler, a large volume of a particularsolution may be dispensed many times. Such bulk dispensation means areknown in the art and can be developed in the future.

The liquid handler may be disposed on a Z-dimensional positioner topermit adjustments in liquid transfer height. This feature allows for alarge range of multiwell plate heights and aspirate and dispense tips,if desired, to be used in the sample distribution apparatus. It alsopermits the dispense distance between a well surface, or liquid surfacein a well, and a liquid handler to be adjusted to minimize the affectsof static electricity, gravity, air currents and to improve the X, Yprecision of dispensation in applications where dispensation of a liquidto a particular location in a well is desired.

Alternatively, multiwell plates can be positioned on a Z-dimensionalpositioner to permit adjustments in liquid transfer height. Staticneutralizing devices can also be used to minimize static electricity.Generally, the liquid transfer height will be less than about 2 cm.Preferably, small volumes will be dispensed at a liquid transfer heightof less than about 10 mm, and more preferably less than about 2 mm.Occasionally, it may be desirable to contact the tips with a solution ina controllable fashion, as described herein or known in the art.

The sample distribution apparatus may also be structured to minimizecontamination. The liquid handler can be constructed to offer minimumtip exposure to liquids using a sensor (e.g., acoustic, and refractiveindex). For instance, probe contact with a liquid surface can be reducedby providing a liquid sensor on the pipetting tip, such as aconductivity or capacitance sensor, that forms a feedback system tocontrol the entrance of a tip into a liquid. Carryover from onemultiwell plate to another multiwell plate can be kept to acceptablelevel with a blow-out of the tip and minimizing tip penetration into aliquid with a sensor. Preferably, a sample distribution apparatus willinclude a means for volume control, and washing the liquid handler.Alternatively, the data processing and integration module can calculatethe remaining levels in the wells based on usage and predictedevaporation, in order to deploy the tips to suitable measured distanceand can be adjusted for multiwell plates of different heights.

In most embodiments, it will be advantageous to integrate and operablylink the sample distribution apparatus with at least one otherworkstation. The integration can be accomplished with a computer andassociated control programs to instruct and coordinate the functions ofthe liquid handler. For implementation with a liquid processing system,a data processing and integration module type device may be used asdescribed herein, as well as other computing devices capable ofintegrating instrumentation as known in the art or developed in thefuture.

Alternatively, a reaction module may be used without directlyintegrating to another workstation by tracking addressable wells ingroups and either mechanically or manually transporting addressablewells to another workstation where the addressable wells are identified.For instance, the reaction module may be directly integrated andoperably linked to a storage and retrieval module and sampletransporter, and indirectly linked to a separate detector through manualoperations. While this approach is feasible, especially for lowerthroughputs, it is not desirable for higher throughputs as it lacksdirect integration that can lead to faster throughput times. Manualoperations also are more frequently subject to error especially whenprocessing large numbers of samples. Preferably, the reaction module canbe integrated with other workstations and operate in a mode with minimalor substantially no manual intervention related to transferringaddressable wells to other workstations.

As noted above, FIG. 1 and FIG. 2 show one embodiment of a sampledistribution apparatus 200 with a conveyor means 210 comprising arotating band that runs the length of the sample distribution apparatusplatform 220 and can transport multiwell plates. A bar code reader 230registers multiwell plates on the conveyor means. A series of liquidhandlers 240 are disposed along the conveyor means. Addressable wells infour chemical multiwell plates can be simultaneously aspirated from theliquid held in the liquid handlers, and then dispensed in additionalplates. Lids can be removed or replaced by the delidder/lidder 250.Proximal multiwell plate stacker 260 and distal multiwell plate stackers260 can be used temporarily to store multiwell plates, such as chemicaland sample plates, which can facilitate multiwell plate selection. Thesample distribution apparatus can be operably linked to a sampletransporter at an ingress/egress junction 270.

Plate Buffers

As noted and shown in FIG. 1 and FIG. 2, the sample distributionapparatus 200 may also include one or more multiwell plate buffers 260(e.g., stackers). The buffer 260 acts as a temporary storage depot foraddressable wells or multiwell plates. Preferably, plate retrieval froma plate buffer will be predetermined. Multiwell plate retrieval can beeither dependent or independent of the order of selection and can becomputer-controlled. Preferably, the data processing and integrationmodule may include an adaptive processing and or parallel processingroutine to reduce storage and retrieval time, as described herein. It isalso desirable to provide for a routine to reduce transport time of anywell retriever used in a storage and retrieval module. By allowing amultiwell plate buffer to acquire addressable wells as they areretrieved by a storage and retrieval module, the transport routine ofthe storage and retrieval module can be designed to minimize retrievaltime rather than to retrieve addressable wells in a sequential order.Also, a stacker may also be used as a multiwell plate buffer. Typically,a plate stacker will up/down stack multiwell plates of a standardfootprint and with different densities (e.g., deep well (e.g., 5 cm) orshallow well multiwell plates of 96 (e.g., 1 cm), 384, 864, 1536, and3,456 (e.g., 1 to 3 mm) well format or greater (e.g., 9,600). A computercontrol system will track stacker contents. The apparatus 200 may alsoinclude a delidder 250 to remove lids on lidded plates.

Conveying Surface

In one embodiment the invention can be used with a conveying surfacethat can transport addressable wells on multiwell plates, between theinvention and other workstations. Typically, the conveying surface willcomprise at least two parallel sample transporter lanes, and preferablyat least four parallel lanes. Typically, a sample transporter lane cantransport plates in both directions (e.g., north and south movement inthe same lane but at different times) by changing the transportdirection. It will, however, be desirable in some instances to dedicateone or more lanes, to unidirectional transport to reduce transitiontimes associated with changing transport direction. Each lane can bedisposed, with one or more intersections that permits transport ofmultiwell plates in and out of each lane. Such intersection can be usedto route multiwell plates to workstations. Typically, at least one ortwo workstations will be operably linked to the sample transporter,however, more workstations (e.g., 3 to 6 or more) can be operably linkedto obtain maximum benefit from flexible routing with intersections andparallel processing of complex processes.

In one embodiment, the conveying surface is a reduced friction,ortho-multilane conduit. In this embodiment, the conveying surface usesmultiple lanes to transport multiwell plates straight to a destinationpoint, preferably not in a rotary fashion. Such lanes can be used tocreate processing grids comprised of intersections and highways todirect the trafficking of multiwell plates. Preferably, such grids arelocated in the same plane but multi-plane grids can be used. Althoughtransport in each lane can be stopped to permit passage of a multiwellplate through an intersection, each lane is a continuous conduit thatallows multiwell plates to flow. The multiwell plates can rest on amoving surface of the conduit or can be secured either on the conduit'ssurface or side, so long as the conduit's surface allows for transport.For ease of overall operation, the flow of the multiwell plates can becomputer-controlled. In some limited, simple applications a lane may besimply activated or deactivated by the presence of an object as amultiwell plate without utilizing a computer.

Preferably, the conduit uses a surface material to reduce friction tominimize the force required for movement and to increase the smoothnessof transport to reduce spills, contamination, and to allow for settlingof well contents if so desired. Such materials include Teflon andDelrin. The materials can be used as rollers or moveable bases connectedto a track that forms a lane. The transport capacity of the conveyingsurface should be commensurate with the intended throughput of thesystem to which it is operably linked. For instance, the rate ofmultiwell plate transport for standard multiwell plates is typically atleast about 6 meters per minute, and preferably at least about 15 metersper minute. Lanes are typically about 15 to 25 cm in width andpreferably about 1 to 5 meters based in length that may be based onqueuing requirements.

Computer Control

In one embodiment, the screening sample distribution apparatus furtherincludes a programmable logic controller, 282 with ladder logic having aminimum of two RS-232 ports open for external communication andprogramming (or GPIB interfaces). The programmable logic controller withladder logic may also have an Ethernet communication card enabling theprogrammable logic controller to communicate with another computer viatransmission control protocol/internet protocol. The programmable logiccontroller may have four discrete inputs and three discrete outputs openfor handshaking to a conveyor system.

Failure of the sample distribution apparatus to perform any programmedfunction within an allotted time may constitute an error. Performance ofa function outside of measurable parameters may also constitute anerror. Errors may be corrected automatically when within the ability ofthe instrument to do so. The user may be notified of unrecoverableerrors via both the touch screen and the external link. In addition, theapparatus may set the handshaking logic to refuse further multiwellplate input until the error is corrected. For given families of errorconditions, a response may be specified, e.g., for recoverable errors,such as bar code errors. For errors that are automatically recoverable,response parameters may exist to either pause the instrument and reportthe error, to automatically recover from the error, or report/log theerror and resume operation. Recoverable errors will have a time-outfunction to halt recovery, if time exceeds a configurable value. Thecontrol software can control the parameters as specified in Table 1, viaan interface. Level two will facilitate the same function via anexternal computer.

TABLE 1 Aspirate Dispense Bar Code Conveyor Delidder Aspirate RangeDispense Range Stacker Read ON/OFF Up/Down Z Height −30 to 60 Z Height−30 to 60 Up/ (mm) (mm) Down Compare Forward/ Volume (μL) 0 to 200Volume 0 to 200 Reverse (μL) Exception Speed (%) 0 to 100 Speed (%) 0 to100 Overfill 0 to 200 (μL) Air Gap (μL) 0 to 200 Pre-Dispense 0 to 200(μL) Plate/Bath 0 or >0

A sample distribution apparatus can include integrated computer controlfor managing and directing the entire dispense operation. The lineararray pipette and its integrated positioning requirements can usesophisticated computer control for effective operation. The computer notonly monitors the status of key sensors (e.g., reagent bottle pressure,liquid level, multiwell plate position, and positioning limit switches)but also provides the interface for generating specific liquiddispensation patterns and volumes to the high density multiwell plate.Timing of dispensation can be accomplished by a variety of means knownin the art and developed in the future, so long as such timing means aresuitable for the time frame and control desired. For example, theNational Instruments AT-MIO-16XE-50 board can be used as timing means tosend timing signals to two of their AT-DIO-32F boards. The 64 ports onthese 32F boards are kept normally high and send out timed low signals.An inverter board is used to make the timed portion high and these highsignals are used to close high voltage relays (Opto ODC5A) which run thevalves. An OV'R driver (Lee Company cat #DRVA0000010A) is used toprotect the valves from overheating during prolonged open periods.

The software controlling the valves (or pipettes) can be written tointegrate into a screening system or for a standalone use. Software forlaboratory instrumentation is known in the art and can be used. Forexample, software can be written in LabVIEW (National Instruments, TX,USA). The user selects a valve opening time and the valves to be opened.This program can be embedded within a larger program that controls otherfeatures (such as the X, Y positioner) to obtain an automatic pipette.

System Operations

The sample distribution apparatus 200 may be used to perform anydifferent operations. For example, the apparatus may be used as ascreening sample distribution apparatus. A screening sample distributionapparatus permits the preparation of multiwell plates or substrates withsamples including chemicals, such as test chemicals from addressablechemical wells and biological reagents (e.g., cells or isolatedmolecular targets) or polynucleotides. The primary function of thescreening sample distribution apparatus is to rapidly aspirate solutionsfrom one multiwell plate and transfer them into another multiwell plateor substrate. This is usually accomplished with an array of 96 pipettorsarranged in a liquid handling head. Typically the pipettors are designedto be substantially smaller in diameter than that of a 96 well diameterto enable maximum positional flexibility when formating from well sizeand density to a second well density and size. In one embodiment, thearray of pipette heads 247 is most preferably M liquid handlers by Nliquid handlers, wherein M is the number of addressable wells in acolumn on a multiwell plate or an integer multiple thereof and N is thenumber of addressable wells in a row on such multiwell plate or aninteger multiple thereof (wherein M and N preferably have the sameinteger multiple), as described herein. The screening sampledistribution apparatus can be operably linked to other workstations witha sample transporter 300, which is also shown in FIG. 3.

The sample distribution apparatus for both aspiration and dispensing inone embodiment comprises pipettes, stackers, a liquid handler, a readerand a conveyor. In one embodiment, the screening sample distributionapparatus is designed with a liquid handler, having 96-pipettes (pipetteheads) that may use positive displacement disposable tips in 200 μL, 50μL and 20 μL volumes. Presently, a disposable 200 μL tip head candeliver a range of volumes of 1 μL to 200 μL, with precision andaccuracy of 10% at 1 μL to 3% at 200 μL. An optional disposable 20 μLtip can deliver a range of volumes of 0.1 μL to 20 μL, with precisionand accuracy of 10% at 0.1 μL to 3% at 20 μL. The pipette can move inZ-axis (vertical axis, i.e. perpendicular to plane of a floor), which iscontrolled with a Z-positioner and has a travel distance from below aconveyor, to access a wash station or reagent trough, to above theconveyor. Preferably, a lidded deep well multiwell plate can passunderneath (about 3 to 5.5 cm in distance). The dispense axis (the axiswith respect to volume displacement) will be at least 10,000 steps(servo-motor) to displace the full pipetting volume. Dispensing speedsare controlled by positive movement of a shaft and are controllable from1 mm/second to 50 mm/second. The resolution of the z-axis will be atleast 25,000 steps over a 75 mm travel from below the conveyor to afully retracted position.

Positional feedback may be required for both Z and D-axis (dispenseaxis), such as encoders, liquid level and limit switches. Both axes maybe capable of simultaneous and concurrent operation independent of eachother. The pipette assembly must be continuously adjustable (no detentesor stops) in “X” and “Y” with a +/−10.0 mm positioning capability withrespect to a plate conveyor. Pipettes can accommodate a flowing washstation and a refilling reagent trough. The pipettes can accommodate384-well plates, as well as 96-well plates. Pipettes can be a piezodevice or a solenoid described herein or known in the art or developedin the future. The liquid level for both aspirating and dispensing canbe monitored by placing a sensor on or near the tip of the liquidhandler, such as an electrical sensor. For example, the capacitivesensor described in U.S. Pat. No. 5,365,783 (Zweifel) can be used, aswell as other suitable sensors known in the art. Such methods can alsobe applied to other liquid handling devices described herein.

In one embodiment, the screening sample distribution apparatus includesor is designed with a stacker magazine having a capacity of about 50standard multiwell plates. Bi-directional stacking with lidded orunlidded plates is desirable. The stacker magazine typically mayaccommodate either standard height multiwell plates or deep wellmultiwell plates in a given stack, and multiwell plate types willtypically not be mixed in a stack. Further, the screening sampledistribution apparatus may include or is designed with a bi-directionalplate delidder and relidder. The lidder removes and replaces plate lidsat a rate of about 5 to 11 plates per minute in one direction. Thelidder can store approximately 60 lids. Preferably, a modified lid isused to enable robotic manipulation and separation from the multiwellplate.

Methods of Reformatting

Using the present apparatus, a master plate may be distributed into oneor more daughter plates or substrates, for example. The master plate maybe aspirated from one or more of the liquid handlers in the sampledistribution apparatus. Daughter plates may be positioned under thepipettors. If the replicate volume is large, e.g. volume×replicatenumber is greater than the tip volume, then multiple aspirations fromthe master are required. Additionally, it is often faster to bring infour masters and then four daughters (one for each master) and repeatthis process until each master is replicated completely. The master mayalso be 384-well plates and the replicates 96-well plates. In this case,the only difference is that the master must travel under all fourpipettors 240 to access each quadrant.

In another embodiment, the master may be an 864-well plate and have ninedaughters produced. In another example of an application of theapparatus 200, multiple master plates may be positioned under separatepipettors or heads 240 to be pooled into a single daughter. Eachpipettor may dispense to a single daughter. This may be in the samewells or separate wells of a 384-well plate or greater density wellplate. Pooling may also consist of more than four masters being combinedinto a single daughter; this may require the daughter to be sequesteredwhile new masters were aspirated from.

In another example, the sample distribution apparatus can dispensereagents necessary for performing a screen. A sample distributionapparatus can rapidly, accurately and reproducibly dispense solutions inan addressable well in predetermined volumes. The pipette arrays aretypically positioned over the desired wells with an X, Y positioner. Asuitable X, Y positioner preferably, permits the array to be positionedover wells having a density greater than the density of pipetting tips.This exploits the narrow size of the pipettors to allow the sampledistribution apparatus to be used for multiwell plates of different andgreater well densities.

FIG. 7 shows different well densities in relation to different tippositions of a pipette array. A well 1810 is addressed by a possible tip1820 (filled circles). Also shown are tip positions 1830 (open circles)that may or may not address a well depending on the well density. Eachbank shown is an array. The increased spatial density of the pipette andthe increased two dimensional density of the target multiwell platerequire substantial positioning accuracy. The positioning accuracytolerance is typically about 200 microns or less, and preferably about50 microns or less in order to ensure that the proper position in thewells for dispensation can be achieved. This feature enables the rapiddistribution of samples into 2-dimensional arrays of varying densities.

Publications

All publications, including patent documents and scientific articles,referred to in this application are incorporated by reference in theirentirety for all purposes to the same extent as if each individualpublication were individually incorporated by reference.

All headings are for the convenience of the reader and should not beused to limit the meaning of the text that follows the heading, unlessso specified.

We claim:
 1. A chemical solution distribution system for distributingchemical solutions to a plurality of multiwell plates having N wellswith I subsets of M wells, I being an integer and greater than one, thesystem comprising: a plurality of liquid handlers, each said liquidhandler including: a head capable of moving in a Z-direction, said headhaving M pipettes; and a table configured to engage one of saidplurality of multiwell plates and movable in an X-Y plane relative to Z,said table capable of moving to at least I different positions, whereinat each of said at least I different positions, said M pipettes of saidhead are aligned with a different one of said I subsets of M wells ofsaid one of said plurality of multiwell plates, and with the provisothat M is about 864 or less.
 2. The chemical solution distributionsystem of claim 1, wherein said system has I liquid handlers.
 3. Thechemical solution distribution system of claim 1, wherein each of saidplurality of said liquid handlers further includes a wash station belowsaid head, wherein said head is capable of moving said M pipettes intocontact with solution in said wash station.
 4. The chemical solutiondistribution system of claim 2, said system further including acomputational unit to reformat from a first density to a second higherdensity multiwell plate.
 5. The chemical solution distribution system ofclaim 1, said system further comprising at least one stacker, saidstacker capable of storing said plurality of multiwell plates.
 6. Thechemical solution distribution system of claim 1, said system furtherincluding a conveyor belt, said conveyor belt capable of moving at leastone of said plurality of multiwell plates between said plurality of saidliquid handlers and at least one stacker.
 7. The chemical solutiondistribution system of claim 5, wherein each of said plurality ofmultiwell plates has a lid, said system further including a delidder,said delidder capable of removing and replacing a lid on each of saidplurality of multiwell plates and said conveyor belt further capable ofmoving said at least one of said plurality of multiwell plates betweensaid plurality of said liquid handlers, said at least one stacker, andsaid delidder.
 8. A chemical solution distribution system of claim 1,wherein M is equal to 96, N is equal to 384, and there are four liquidhandlers.
 9. The chemical solution distribution system of claim 1, whereM is equal to
 96. 10. The chemical solution distribution system of claim1, where M is equal to 96 and N is equal to one of 384 or
 864. 11. Achemical solution distribution system for distributing chemicalsolutions between at least one first multiwell plate having N wells withI subsets of M wells, I being an integer and greater than one and atleast one solid substrate or at least one second multiwell plate havingM sites or wells, the system comprising: a plurality of liquid handlers,each liquid handling station including: a head capable of moving in aZ-direction, said head having M pipettes; and a table configured toengage one of said at least one first multiwell plate having N wells orsaid at least one second multiwell plate having M wells or said solidsubstrate and movable in an X-Y plane relative to Z, said table capableof moving to at least I different positions, wherein at least at Idifferent positions, said M pipettes of said head are aligned with adifferent one of the I subsets of M wells of the at least one multiwellplate having N wells or at least at one position said M pipettes of saidhead are aligned with said M wells of said at least one solid substrateor at least one second multiwell plate having M sites or wells, and withthe proviso that M is about 864 or less.
 12. The chemical solutiondistribution system of claim 11, wherein said table is movable to I plusone positions.
 13. The chemical solution distribution system of claim12, wherein M is equal to
 96. 14. The chemical solution distributionsystem of claim 13, wherein N is equal to one of 384 or
 864. 15. Thechemical solution distribution system of claim 13, wherein there are Iliquid handlers.
 16. A method of distributing chemical solutions betweena plurality of plates having N wells with I subsets of M wells, I beingan integer and greater than one, said method comprising the steps of:aligning a subset of M wells of a first one of said plurality of plateswith M pipettes of a first pipette station; lowering said M pipettes ofsaid first pipette station to engage said subset of M wells andaspirating solution from M wells into said M pipettes and dispensingsolution from said M pipettes into a first set of M wells; aligning asubset of M wells of a second one of the plurality of plates with Mpipettes of a second pipette station; and lowering said M pipettes ofsaid second pipette station to engage said subset of M wells of saidsecond one of the plurality of plates and one of aspirating solutionfrom M wells into said M pipettes and dispensing solution from said Mpipettes into a second set of M wells, and with the proviso that M isabout 864 or less.
 17. The method of claim 16, wherein said samples arechemicals and said plurality of multiwell plates are used to store testchemicals.
 18. The method of claim 17, wherein said chemicals comprisepolynucleotides.
 19. The method of claim 17, further comprising the stepof providing a different solution to wash stations of the first liquidhandler and said second liquid handler.
 20. The method of claim 16,further comprising the steps of: aligning a subset of M wells of a thirdone of said plurality of plates with M pipettes of a third pipettestation; lowering said M pipettes of said third pipette station toengage the subset of M wells of said third one of said plurality ofplates and one of aspirating solution from M wells into said M pipettesand dispensing solution from said M pipettes into a third set of Mwells; aligning a subset of M wells of a fourth one of said plurality ofplates with M pipettes of a fourth pipette station; and lowering said Mpipettes of said fourth pipette station to engage the subset of M wellsof said fourth one of said plurality of plates and one of aspiratingsolution from M wells into said M pipettes and dispensing solution fromsaid M pipettes into a fourth set of M wells.
 21. A method ofdistributing chemical solutions to a first plate having N wells with Isubsets of M wells, I being an integer and greater than one and at leastone second plate with about N/I wells, the method comprising the stepsof: aligning a first subset of N/I wells of said first plate with Mpipettes of a first pipette station; lowering said M pipettes of saidfirst pipette station to engage said first subset of N/I wells andaspirating solution from said N/I wells into said M pipettes anddispensing solution from said M pipettes into a subset of M wells;aligning a second set of N/I wells a second plate with M pipettes of asecond pipette station; and lowering said M pipettes of said secondpipette station to engage said second set of N/I wells of said secondplate and aspirating solution from said N/I wells of said second plateinto said M pipettes and dispensing solution from said M pipettes into asecond subset of M wells and with the proviso that M is about 864 orless.
 22. The method of claim 21, further comprising the steps of:aligning a third set of N/I wells of one of said plurality of plateswith M pipettes of a third pipette station; lowering said M pipettes ofsaid third pipette station to engage said third set of N/I wells andaspirating solution from M wells into said M pipettes and dispensingsolution from said M pipettes into a third set of M wells; aligning afourth subset of N/I wells of one of said plurality of plates with Mpipettes of a fourth pipette station; and lowering said M pipettes ofsaid fourth pipette station to engage said fourth set of N/I wells ofone of said plurality of plates and aspirating solution from M wellsinto said M pipettes and dispensing solution from said M pipettes into afourth set of M wells.
 23. The method of claim 22, further comprisingthe step of providing a different solution to wash stations of saidfirst liquid handler, said second liquid handler, said third liquidhandler, and said fourth liquid handler.
 24. The method of claim 23,wherein M is equal to
 96. 25. The method of claim 24, wherein N is equalto one of 384 or
 864. 26. A chemical solution distribution system fordistributing chemical solutions into multiwell plates having at least384 wells, the system comprising: a) at least one liquid handlercomprising 48 or more, but less than 384, tips, said tips having adynamic range of liquid dispensation of 100 to 2000 nanoliters, and b)an orthogonal positioner, said liquid handler comprising a tipdispensing matrix with about 96 or more tips, being capable of movingsaid at least one multiwell plate with an X-Y location accuracy of atleast ±0.09 mm in X and Y.
 27. The device of claim 26, wherein saidliquid handler comprises a tip dispensing matrix with about 96 or moretips.
 28. The device of claim 27, wherein said tip dispensing matrixcomprises no more than 96 tips.
 29. A test chemicals distribution systemfor distributing test chemicals to a plurality of multiwell plates usedto store chemical libraries having N wells with I subsets of M wells, Ibeing an integer and greater than one, the system comprising: aplurality of liquid handlers containing test chemicals, each said liquidhandler including: a head capable of moving in a Z-direction, said headhaving M pipettes; and a table configured to engage one of saidplurality of multiwell plates and movable in an X-Y plane relative to Z,said table capable of moving to at least I different positions, whereinat each of said at least I different positions, said M pipettes of saidhead are aligned with a different one of said I subsets of M wells ofsaid one of said plurality of multiwell plates, and with the provisothat M is about 864 or less.
 30. A chemical solution distribution systemfor distributing chemical solutions comprising polynucleotides to aplurality of multiwell plates having N wells with I subsets of M wells,I being an integer and greater than one, the system comprising: aplurality of liquid handlers containing chemical solutions comprisingpolynucleotides, each said liquid handler including: a head capable ofmoving in a Z-direction, said head having M pipettes; and a tableconfigured to engage one of said plurality of multiwell plates andmovable in an X-Y plane relative to Z, said table capable of moving toat least I different positions, wherein at each of said at least Idifferent positions, said M pipettes of said head are aligned with adifferent one of said I subsets of M wells of said one of said pluralityof multiwell plates, and with the proviso that M is about 864 or less.